Gas meter temperature compensating tangents

ABSTRACT

A gas meter temperature compensating tangent device having a tangent block to which is adjustably connected a tangent arm for journaling a crankshaft. The tangent block has a guideway formed in alignment with the axial line of the tangent arm. A plurality of nested &#34;U&#34; shaped bi-metal strips have one end pivotably connected to the tangent block and the other end connected to a tangent wrist which is slideably disposed in the guideway. The bi-metal strips will sense temperature changes in the gas and force the tangent wrist to slide in the guideway to increase or decrease the distance between the tangent wrist and the crankshaft. 
     The tangent device provides improved accurate deflection due to temperature changes as a result of built-in radial rigidity of the tangent wrist relative to the tangent arm.

BACKGROUND OF THE INVENTION

One convenient form of compensation for the change in gas volume due to temperature is to detect the gas flowing temperature and to continuously adjust the meter accuracy such that the read-out reflects the measured volume at a base temperature. However stability of the temperature-correcting systems used in the prior art has been less than perfect, and such systems have often encountered accuracy problems due to binding, hysteresis losses and inaccurate deflection caused by conflicts in the direction of movement of the bi-metal and the tangent block component relative to the position of the crankshaft or the tangent arm journaling the same. Such problems are compounded as the size of the meter increases in that the required deflection also increases, along with the forces.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel gas meter temperature compensating tangent which is an improvement over the prior art; which is simple, economical and reliable; which has a radially rigid guideway which permits accurate deflection due to temperature change in the gas flowing temperature; which uses a tangent block having a radial guideway axially aligned with the tangent arm and in which is disposed a tangent wrist connected to the bi-metal member the other end of which is hinge connected to the tangent block; which uses "U" shaped bi-metal strips having one end hinge connected to the tangent block and the other end connected to the tangent wrist; which uses a roller movably mounted in the radial guideway; and which uses a radial guideway having an axis substantially coincident to or parallel to the axis of the tangent arm.

Other object and advantages will be apparent from the following description of one embodiment of the invention and the novel features will be particularly pointed out hereinafter in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention is illustrated in the accompanying drawings in which:

FIG. 1 is a top plan view of a gas meter showing the gas distribution chamber in which the present invention is embodied.

FIG. 2 is a top plan view of the gas meter temperature compensating tangent of the present invention,

FIG. 3 is a side elevational view of the gas meter temperature compensating tangent of the present invention,

FIG. 4 is a top plan view of the gas meter temperature compensating tangent showing the tangent wrist in two positions with the solid line representation depicting a lower gas temperature and dotted line representation depicting a higher gas temperature.

DESCRIPTION OF THE INVENTION

In the illustrated embodiment of the invention a gas meter 10 is shown in FIG. 1 with the cover removed to expose the gas distribution chamber 12 having an inlet at 14 and an outlet at 16. The valve chambers are depicted generally at 18, 18 on the outlet side of the chamer 12, while the flag rods 20, 20 are shown on the inlet side of the chamber 12 at opposite ends thereof. Flag arms 22, 22 are affixed at one end to the flag rods 20, 20 and the other end carry links 24, 24 which each connect to a tangent wrist 26. The tangent wrist 26 is connected to the tangent device, designated generally 28, to which a crankshaft 30 is also connected as described more fully hereinafter to drive the slide valves 32, 32 which controls and synchronized the flow to and from the valve chambers 18, 18 as to measure the thruput flow of gas from the inlet 14 to the outlet 16.

The tangent device or tangent 28 is shown in FIGS. 2 and 3, and in the gas meter art serve to fix the length of the stroke of the flag rods 20, 20 and the timing of the valves 32, 32.

The tangent device illustrated in FIGS. 2 and 3 includes a tangent arm 34 which is mounted for universal adjustment to a tangent block 36 at the base 38 thereof. The tangent arm 34 has a rounded end 40 with a through aperture 42 in which the crankshaft 30 is journaled. A shank 44 having slabbed sides 46 and threaded corners 48 extends from the end 40 to and through the base 38 wherein the tangent arm 34 is connected by means of locking nuts 50 disposed on either side thereof. The base 38 is fitted with a transverse slot seen best in FIG. 3 through which the tangent arm 34 extends to be shifted by a pair of timing-adjustment screws 54 within the slot 52. The tangent arm 34 has an axis 56 which substantially intersects the axis 58 of the crankshaft 30 as illustrated in FIG. 2. Thus, the tangent arm 34 may be shifted along its axis 56 by manipulating the nuts 50, or the axis 56 may be transversely shifted along the base 38 by manipulation of the screws 54. In either case, the crankshaft 30 being journaled by the tangent arm 34 will be likewise shifted relatively with the tangent arm 34. The adjustment of the tangent arm 34 is necessary to obtain the correct registration of the volume of gas. Adjustment of the tangent arm 34 along its axis 56 will change the distance between the tangent wrist 26 and the crankshaft 30, which distance controls the stroke of the gas measuring diaphrams. The transverse shifting of the axis 56 within the slot 52 serves to adjust the angular relationship of the tangent wrist 26 to the crankshaft 30 so as to be control the valve timing. When both the stroke of the tangent wrist 26 and the angular relationship of the tangent wrist 26, relative to the crankshaft 30, are correctly adjusted, the meter 10 will accurately measure the volume of gas.

Another factor to be considered in obtaining an accurate measurement of the quanitity of gas passing through the meter is that the density of the gas varies with temperature. Therefore, change in the density of the gas due to change in temperature must be compensated for. This may be done at the tangent device 28. The present tangent device 28, as shown in FIGS. 2, 3 and 4, will provide for temperature compensation due to changes in gas density or other affects of temperature change such as valve friction and/or diaphram stiffness, and the like.

The tangent block 36 has a guide frame 60 which extends from one side of the base 38 at either end thereof to form a large lower hollow 62, the opening of which is sufficiently large to permit the complete range of adjustments of the tangent arm 34 whether for timing or stroke. A guideway 64 is formed at the end of the guide frame 60 remote from the base 38 and runs inwardly from its outer end to communicate with the hollow portion 62. The guideway 64 has an axis 66 which is substantially perpendicular to the base 38, and will extend therefrom as would a radial line from the center of a circle. The axis 66 is formed to align with the axis 56, whether coincident or parallel thereto.

The width of the guideway 64 is sufficiently large to receive a guide roller 68 which is sized for sliding movement therein. The guide roller 68 has an upper edge 70 which overlaps the side wall of the guideway 64 to prevent the roller from dropping vertically downwardly through the guideway 64. Extending upwardly from the internal periphery of the edge 70 is a sleeve 72 in which the tangent wrist 26 is disposed to intersect its axis 74 with the axis 66 of the guideway 64 as illustrated in FIGS. 2 and 3. The under side of the guide roller 68 is connected to one end of a "U" shaped bi-metal temperature sensitive member 76 which includes a plurality of nested bi-metal strips 78, which strips increase in thickness in the direction toward the outer strip so that all of the strips will deflect equally at the tangent wrist 26 attachment. Of course, in those applications which require only a single strip 78 the bi-metal member 76 would be of uniform thickness. The bi-metal member 76 will prevent the roller 68 from vertically upward movement when the roller 68 is assembled in the guideway 64.

The bi-metal member 76 would form an integral sub-assembly including the roller 68, the bi-metal strips 78 which at the end opposite the roller 68 the strips would connect to a pivot block 80 which is hinge connected by a frame screw 82 to define a pivot axis 84 shown in FIGS. 2 and 3. The axis 58 of the crankshaft 30 is disposed parallel to an intermediate of the axis 74 of the tangent wrist 26 and the pivot axis 84. The bi-metal member 76 as illustrated in FIG. 4 will automatically lengthen the stroke when the gas temperature is higher as represented by the dotted line position of the guide roller 68 which places the axis 74 of the tangent wrist 26 at a greater distance from the axis 58 of the crankshaft 30. This occurs responsive to the distance between the opposite legs of the bi-metal strips 78 becoming greater. Upon the gas temperature decreasing the bi-metal strips 78 of the bi-metal member 76 will automatically deflect to be drawn closer to each other and thereby place the guide roller 68 and the solid line position illustrated in FIG. 4 so as to shorten the stroke by placing the axis 74 of the tangent wrist 26 at a closer distance to the axis 58 of the crankshaft 30. The sliding motion of the guide roller 68 will cause a slight rotation of the pivot block 80 about the pivot axis 84. An angle "A" if formed with its center coincident to the axis 74 of the tangent wrist 26 and with one of its legs lying on the axis 66 and the other leg formed by passing a line between the axes 74 and 84. It will be noted that the variations of any angular difference in the angle "A" caused by change of the temperature of the gas producing temperature shifts of the bi-metal member 76 is illustrated if FIG. 4 will be very small so as to render any pivotal motion about the pivot axis 84 to be negligible.

It is important to maintain the stability of the temperature correcting system in order to provide consistantly accurate measuring by the meter. Also, as the size of the meter increases so does the deflection of the temperature correcting system and any resultant forces related thereto. A greater deflection requires longer and thinner bi-metal strips which serve as the temperature detecting medium and which act to reduce the rigidity thereof. Another consideration is that with the improved tangent device of the present invention a similar deflection to the prior art can be obtained with less bi-metal material, a greater rigidity and a cost savings in bi-metal material.

By confining the guide roller 68 within the radial guide way 64 its sliding movement due to temperature change in the gas is restricted to correspond to the axis 66 of the guideway which lies substantially perpendicular to the base 38, and therefore, may be termed "radial" accordingly the novel tangent device 28 provides for a higher degree of rigidity and consistancy of accuracy and wear reduction than was possible in prior art temperature compensated tangents. Upon a stroke or accuracy correction to compensate for the temperature effect of the gas being made by the bi-metal member 76 moving the tangent wrist 26 within the radial guideway 64 the radial forces created by the slight rotation of the pivot block 80 about the pivot axis 84 will be transmitted to the tangent block 36 so as to result in a system of high rigidity and low hysteresis. By providing a radial guideway 64 in the same direction as the major forces which would be created by any temperature compensation the movement of the guide roller 68 caused by the response of the bi-metal 76 to temperature change is free of any binding, unguided deflection or hysteresis loss. Also, the use of the pivot block 80 to rotate about the pivot axis 84 aids in the free and urestricted movement of the bi-metal member 76.

It will be understood that there is changes in the details, materials, arrangements of arts and operating conditions which have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art within the principles and scope of the invention. 

Having thus set forth the nature of the invention, what is claimed herein is:
 1. A temperature compensating tangent device for a gas meter comprising:a. a tangent block, b. a tangent arm having a longitudinal axis connected to the tangent block, c. a crank shaft connected to the tangent arm, d. a guideway formed in the tangent block in substantial alignment with the axis of the tangent arm, e. a guide roller directly connected in and shiftable along the length of the guideway, f. a tangent wrist affixed to the guide roller, g. a bi-metal member asymmetrically connected between the tangent block and the guide roller, with the tangent block connection being pivotal, h. the bi-metal member including a plurality of substantially "U" shaped nested bi-metal strips of varying thickness to expand or contract responsive to temperature changes of the gas flowing through the meter, and i. the bi-metal member to cause the guide roller to continuously move along the guideway to increase or decrease the distance between the tangent wrist and the crank shaft continuously to adjust the position of the tangent wrist relative to the crank shaft.
 2. The combination claimed in claim 1 wherein:a. the tangent block is formed with a hollow interior, b. a base formed on one side of the tangent block, c. the tangent arm connected to the base, with the crank shaft connection disposed in the hollow interior of the tangent block, d. the guideway formed in the hollow interior of the tangent block on the side thereof remote from the base, and e. the guide roller disposed to be continuously shiftable with the guideway formed in the hollow interior of the tangent block.
 3. The combination claimed in claim 2 wherein:a. the bi-metal member having one end pivotally connected to the base of the tangent block on one side of the tangent arm, and the other end thereof connected to the guide roller, and b. the open end of the "U" shaped bi-metal member substantially facing in the direction of the hollow interior of the tangent block. 